Ubuntu OS

Ubuntu Touch is a mobile interface for Ubuntu developed by Canonical Ltd. for smartphones and tablets. Ubuntu Touch aims to provide a similar user experience as the Unity desktop. The interface was previewed on 2 January 2013 and it has been released as a Developer Preview in February 2013.
Ubuntu Touch utilizes the same core technologies as the Ubuntu
Desktop, so applications designed for the latter platform run on the
former and vice versa. Additionally, Ubuntu Desktop components come with
the Ubuntu Touch system; allowing Ubuntu Touch devices to provide a
full Unity experience when connected to an external monitor. --readmore

Firefox OS

Firefox OS (project name: Boot to Gecko also known as B2G) is a Linux-based open source operating system for smartphones and tablet computers being developed by Mozilla. It is designed to allow HTML5 applications to communicate directly with the device's hardware using JavaScript.It has been demonstrated on Android-compatible smartphones, and the Raspberry Pi.
The first smartphones running Firefox OS should be released in the
first half of 2013 (expecting July, 2013). It will first be released in
South America, and will later come to Asian and European markets. ZTE confirmed at CES 2013 that they will ship a smartphone with the OS. --readmore

Tizen OS

Tizen (/ˈtaɪzɛn/) is an operating system for devices including smartphones, tablets, in-vehicle infotainment (IVI) devices, and smart TVs. It is an open source system that aims to offer a consistent user experience across devices. Tizen's main components are the Linux kernel and the WebKit runtime. The Tizen project resides within the Linux Foundation and is governed by a Technical Steering Group (TSG) composed of Intel and Samsung. --readmore